Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$217.79	5.297%	$229.3263	$229.33	$229.35	$229.30
Purchase #2	$29.39	10.829%	$32.5726	$32.57	$32.55	$32.60
Purchase #3	$209.77	5.590%	$221.4961	$221.50	$221.50	$221.50
Purchase #4	$23.52	5.576%	$24.8315	$24.83	$24.85	$24.80
Purchase #5	$29.69	10.571%	$32.8285	$32.83	$32.85	$32.80
Purchase #6	$38.68	12.755%	$43.6136	$43.61	$43.60	$43.60
Purchase #7	$178.51	3.343%	$184.4776	$184.48	$184.50	$184.50
7 purchase totals =	$727.35		$769.1462	$769.15	$769.20	$769.10